1. Field of the Invention
The present invention relates to a conical nib and a writing instrument using the same.
More particularly, the invention relates to a conical nib with parts assembled with high precision and a writing instrument using the same.
2. Description of the Related Art
A writing instrument including such a nib is described in Patent Literature 1. The nib of the writing instrument described in Patent Literature 1 is provided with a nib base body and a converging member. The nib base body is constituted by a cylindrical base portion and five to eight combtooth-like pieces. The combtooth-like pieces, each having an arc-shaped cross section, extend continuously from one end of the cylindrical base portion. The combtooth-like pieces are arranged at equal intervals on the circumference of the cylindrical base portion and are divided by slits. The combtooth-like pieces define a hemisphere-divided portion at tips thereof. The converging member is a metal pipe capable of fitting onto an outer periphery of the nib base body. When the converging member is fit onto the nib base body, the combtooth-like pieces are gradually tapered toward the tips thereof to form a conical shape. A hemispherical writing tip is defined at the tips of the combtooth-like pieces and ink feed paths are defined between adjacent combtooth-like pieces. An ink relay core having capillary action to a front end thereof is inserted in a hollow of the nib (i.e., the nib base body). The ink relay core is integrally fixed to the front end of a pen shaft and the ink relay core is connected to the ink reservoir inside the pen shaft. The thus-structured nib can be used to write in many directions on a paper sheet. The nib can be used to write at any positions and at any angles, even if the nib is rotated about the pen shaft. Various characters, i.e., characteristics of varying width, can be written in accordance with varying writing pressure.
A related art of the present technique is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 9-156279.
However, the writing instruments using such conical nibs have difficulty in tip alignment with high precision at the writing tip of the nib and have difficulty in achieving roundness of the nib piece. Thus, there are problems of less smoothness in writing, scratchy writing or a leakage of ink.
Another problem relates to the space inside the nib, i.e., the space between the nib and the ink relay core. If the pen is kept with the nib facing downward with the ink accommodated in the ink reservoir, the ink is collected inside the nib (i.e., the space between the nib and the ink relay core) due to the gravity and capillary action of the ink at the nib (i.e., the ink feed path) and of the ink relay core. If the amount of ink is substantially full of the ink reservoir, there is no (or small, if any) expansion of air resulting from the change in temperature or pressure inside the ink reservoir and thus no leakage of ink occurs; but if the amount of ink is reduced less than half the ink reservoir, expansion of air resulting from the change in temperature or pressure in the ink reservoir becomes greater, and the air pressure may cause a leakage of ink.
The present invention is made to solve these related art problems. A first object of the present invention is to provide a conical nib with a writing tip manufactured with increased precision and a writing instrument using the conical nib.
A second object is to form a nib piece with high roundness and to increase processability in bending and shaping a punched plate during the manufacture of the nib piece.
A third object is to provide a highly rigid structure of the nib piece by holding each part of the nib piece with greater force.
A fourth object is to prevent accumulation of ink in a space between the nib and the ink relay core and to thereby prevent a leakage of ink in this kind of writing instrument.